1. Field of the Invention
The present invention relates to a stage unit and an exposure apparatus. More particularly, it relates to an exposure apparatus that performs exposure on a substrate with an energy beam so as to form a predetermined pattern on the substrate and a stage unit that can be suitably applied to the exposure apparatus.
2. Description of the Related Art
Conventionally, in a lithographic process to manufacture devices such as a semiconductor device or a liquid crystal display device and the like, an exposure apparatus is used that transfers a pattern formed on a mask or a reticle (hereinafter generally referred to as a xe2x80x9creticlexe2x80x9d) onto a wafer or a glass plate (hereinafter generally referred to as a xe2x80x9cwaferxe2x80x9d) via a projection optical system. In recent years, due to higher integration of the semiconductor device, the type of projection exposure apparatus that moves step by step such as the reduction projection exposure apparatus based on the step-and-repeat method (the so-called stepper) and the scanning type projection exposure apparatus, which is an improvement of the stepper, based on the step-and-scan method (the so-called scanning stepper) or the like has become mainstream.
The semiconductor device or the like is made by overlaying patterns in multiple layers, therefore, with the exposure apparatus such as the stepper the overlay of the pattern formed on the reticle onto the pattern already formed on the wafer needs to be highly accurate. This requires a precise measurement of the position on the wafer of the shot area where the pattern is formed, and for the precise measurement a method that uses a variety of position measurement sensors to measure the position of alignment marks arranged along each shot area is employed.
Furthermore, for this measurement, as a reference for measuring the positional relationship between the reticle, the projection lens, and the wafer a fiducial mark plate on which various types of fiducial marks are formed is arranged in the vicinity of the wafer on the wafer stage that holds the wafer.
Normally, one fiducial mark plate is arranged on the wafer stage, and by measuring the fiducial marks formed on the fiducial mark plate the relative distance between position measurement sensors is controlled as well as the orthogonal degree of the stage interferometer that measures the position of the stage and the conversion rate used to figure out the distance from the interference fringe count measured with the stage interferometer.
In the case, however, when measurements for these controls are performed using a single fiducial mark plate, the measurement accuracy may decrease since the span of the measurement distance is limited by the size of the fiducial mark plate.
Therefore, as a means of improving the measurement accuracy, the possibility of increasing the size of the fiducial mark plate can be considered, however, this may lead to a larger stage size. Especially, with the exposure apparatus recently gathering attention that comprises a plurality of substrate stages, since the stages require an extremely large driving range the footprint of the apparatus naturally has to increase, thus causing an inconvenience.
Furthermore, with the exposure apparatus comprising a plurality of substrate stages as is referred to above, in most cases the exposure apparatus comprises only one optical system for exposure, and in such a case there is a tendency of the exposure position and the alignment position being far apart so as to prevent interference between stages from occurring. This makes the optical axis of the interferometer measuring the position of the stage between the exposure position and the alignment position stray from the stage, nevertheless, even in such a case, the positional relationship of the substrate on the stage with respect to the optical system for exposure and the mask must be controlled with good accuracy.
The present invention has been made in consideration of the circumstances described above, and has as its first object to provide a stage unit that can be downsized while maintaining its measurement performance.
It is the second object of the present invention to provide an exposure apparatus which substrate stage can be downsized as well as the footprint of the apparatus reduced.
And, it is the third object of the present invention to provide an exposure apparatus which substrate stage can be downsized and the footprint of the apparatus reduced, and is also capable of controlling the position of the substrate with good accuracy at all times.
According to the first aspect of the present invention, there is provided a stage unit comprising: a substrate holding member which holds a substrate; and a substrate stage which moves two dimensionally with the substrate holding member mounted, and on which a plurality of fiducial marks are arranged dispersed by each measurement sequence which uses the fiducial marks with a positional relationship between each of said fiducial marks and the substrate holding member constant.
With this stage unit, a plurality of fiducial marks are arranged dispersed by each measurement sequence which uses the fiducial marks and the positional relationship between each of the fiducial marks and the substrate holding member is constant. Therefore, for example, the fiducial marks can be respectively arranged apart at a certain interval on the periphery of the substrate holding member. This makes it possible to sufficiently secure the interval (distance) between the fiducial marks, relax the limitations on the measurement span, and consequently, improve the measurement accuracy. In addition, the respective fiducial marks can be arranged on the substrate stage even when the space is small. Since the plurality of fiducial marks are arranged dispersed by each measurement sequence which uses the fiducial marks, the performance regarding measurement can be maintained. Accordingly, the stage can be downsized, maintaining its measurement performance.
In this case, the plurality of fiducial marks can be at least three fiducial marks respectively arranged in the vicinity of each vertex position of a polygon, which contains a center of the substrate holding member. In such a case, the center of the substrate holding member lies within the area of the polygon surrounded by the fiducial marks, therefore, in the case of obtaining the center of the substrate holding member based on the measurement results of the position of the fiducial marks, the central point corresponds, so to speak, to the interpolation point of the fiducial mark positions. Accordingly, by performing a predetermined calculation based on the positional information on the fiducial marks, the holding member coordinate system which origin is the center of the substrate holding member can be obtained with a sufficient level of reliability.
With the stage unit according to the present invention, the plurality of fiducial marks can include a first fiducial mark and a second fiducial mark, which are arranged on a straight line passing through a center of the substrate holding member on opposite sides with respect to the center. In such a case, since the first fiducial mark and the second fiducial mark are arranged on a straight line passing through the center of the substrate holding member on opposite sides with respect to the center, the interval between both fiducial marks can be around the diameter length of the substrate holding member, which relaxes the limitations on the measurement span, and consequently, the measurement accuracy can be improved. In addition, since the two fiducial marks are symmetric with respect to the center of the substrate holding member, it is possible, for example, to easily calculate the center coordinate and the rotational angle of the substrate holding member.
With the stage unit according to the present invention, each fiducial marks may be formed directly on the substrate stage, however, the stage unit may further comprise: a plurality of fiducial mark plates arranged on a periphery of the substrate holding member on the substrate stage, on which at least one of the fiducial marks is respectively formed.
According to the second aspect of the present invention, there is provided a first exposure apparatus which exposes a substrate with an energy beam and forms a predetermined pattern on the substrate, the exposure apparatus comprising: a substrate stage that moves two-dimensionally; a substrate holding member mounted on the substrate stage that holds the substrate; a plurality of fiducial mark plates on which a plurality of fiducial marks are dispersedly arranged by each measurement sequence which uses the fiducial mark plates, and are arranged on a periphery of the substrate holding member on the substrate stage with a positional relationship between each of said fiducial marks and the substrate holding member constant; a mark detection system which detects marks located on the substrate stage; and a control unit, which performs various types of measurement sequences respectively including a detection operation to detect at least one of the plurality of fiducial marks using the mark detection system.
With this exposure apparatus, a plurality of fiducial mark plates on which a plurality of fiducial marks are arranged by each measurement sequence which uses the fiducial mark plates on the periphery of the substrate holding member, and the positional relationship between each fiducial mark and the substrate holding member is constant. This allows the fiducial mark plates to be arranged on even a small space on the substrate stage. Furthermore, since the control unit performs various types of measurement sequences respectively, including the detection operation to detect at least one of the pluralities of fiducial marks, the performance related to measurement can be maintained. Accordingly, it becomes possible to downsize the substrate stage, and in turn, to reduce the footprint of the apparatus, while maintaining its measurement performance.
In this case, when the exposure apparatus further comprises: a position measurement unit that controls a position of the substrate stage based on an orthogonal coordinate system, the plurality of fiducial mark plates can include a first mark plate on which a plurality of fiducial marks are arranged along a first axis direction of the orthogonal axis, the first mark plate narrowly extending in the first axis direction, and a second mark plate on which a plurality of fiducial marks are arranged along a second axis direction orthogonal to the first axis, the second mark plate narrowly extending in the second axis direction.
In this case, when the exposure apparatus further comprises: a mask stage that holds a mask on which the pattern is formed; a drive unit which synchronously moves the mask stage and the substrate stage along the second axis direction; and a pair of mark detection systems for masks that measure at least one pair of mask marks formed on both sides of the pattern on the mask in the first axis direction, a length of the first mark plate in the first axis direction can almost correspond to a distance between the pair of mask marks, and a length of the first mark plate in the second axis direction can be slightly longer than a length required to form the fiducial mark. In such a case, it becomes possible to form a pair of fiducial marks that can be measured at the same time with the pair of mask marks detected with the pair of mark detection systems on the first mark plate.
In addition, with the first exposure apparatus according to the present invention, in the case of comprising the position measurement unit, the first mark plate, and the second mark plate, when the exposure apparatus further comprises: a mask stage that holds a mask on which the pattern is formed; a drive unit which synchronously moves the mask stage and the substrate stage along the second axis direction; a mask side position measurement unit which measures a position of the mask stage; and a mark detection system for masks which measures a plurality of pairs of mask marks formed on both sides of the pattern on the mask in the first axis direction, a length of the second mark plate in the second axis direction can almost correspond to a length of the pattern in the second axis direction, and a length of the second mark plate in the first axis direction can be slightly longer than a length required to form the fiducial mark. In such a case, it becomes to possible to form a fiducial mark that can be used for scaling adjustment between the mask side position measurement unit and the position measurement unit that measures the position of the substrate stage using one of the detection systems for masks, on the second fiducial mark plate.
According to the third aspect of the present invention, there is provided a second exposure apparatus which exposes a substrate with an energy beam and forms a predetermined pattern on the substrate, the exposure apparatus comprising: a substrate stage that moves two-dimensionally; a position measurement unit that measures a position of the substrate stage; a substrate holding member mounted on the substrate stage that holds the substrate; at least three fiducial marks that are respectively arranged in the vicinity of each vertex position of a polygon that contains a center of the substrate holding member, and are arranged on the substrate stage with a positional relationship between each of said fiducial marks and the substrate holding member constant; a mark detection system which detects marks located on the substrate stage including the fiducial marks; and a control unit that performs various types of measurement sequences respectively including a detection operation to detect either of one and a plurality of at least three fiducial marks using the mark detection system and the position measurement unit.
With this exposure apparatus, since the respective fiducial marks are arranged in the vicinity of each vertex of the polygon, the interval (distance) between the fiducial marks can be sufficiently large, and limitations on the measurement span can be relaxed, allowing the measurement accuracy to be improved. In addition, the center of the substrate holding member lies within the area of the polygon surrounded by the fiducial marks, therefore, in the case of obtaining the center of the substrate holding member based on the measurement results of the position of the fiducial marks, the central point corresponds, so to speak, to the interpolation point of the fiducial mark positions. Accordingly, the controller can, for example, detect the positional information on each fiducial mark arranged on the substrate stage by using the mark detection system and the position measurement, and by performing a predetermined calculation based on the positional information, the holding member coordinate system which origin is the center of the substrate holding member can be obtained with a sufficient level of reliability. Furthermore, the control unit obtains the positional information on the alignment marks that lie within the polygon on the substrate using the mark detection system and the position measurement unit based on an arbitrary coordinate system, such as the stage coordinate system, and converts the information to the positional information based on the holding member coordinate system. This allows the fiducial marks to be re-measured based on a new coordinate system, even in the case when the position of the substrate stage cannot be controlled temporarily, and based on the measurement results and the positional information based on the holding member coordinate system, the positional information on the alignment marks can be obtained with high reliability based on the new coordinate system. Accordingly, for similar reasons explained earlier, it becomes possible to control the position of the substrate with good accuracy at all times, without increasing the size of the substrate stage and the footprint of the apparatus.
In this case, each of the fiducial marks may be formed directly on the substrate stage, however, for example, the exposure apparatus may further comprise: a plurality of fiducial mark plates on which at least one of the fiducial marks is respectively formed, the fiducial mark plates arranged on a periphery of the substrate holding member on the substrate stage.
In this case, the at least three fiducial marks can be arranged on the plurality of fiducial mark plates, dispersed by each measurement sequence which uses at least one of the fiducial marks. In such a case, by dispersing the marks that normally are located in large numbers on the fiducial mark plate by their measurement sequences, the fiducial mark plates can each be downsized while maintaining its functions, and as a consequence, the substrate stage on which the fiducial mark plates are arranged and the whole exposure apparatus can be downsized.
In this case, a position of the substrate stage is controlled with the position measurement unit based on an orthogonal coordinate system, and the plurality of fiducial mark plates can include a first mark plate on which a plurality of fiducial marks are arranged along a first axis direction of the orthogonal axis, the first mark plate narrowly extending in the first axis direction, and a second mark plate on which a plurality of fiducial marks are arranged along a second axis direction orthogonal to the first axis, the second mark plate narrowly extending in the second axis direction. In such a case, by dispersing the fiducial marks existing in large numbers by their measurement sequences, the fiducial mark plates can each be downsized while maintaining the performance, and as a consequence, the substrate stage on which the fiducial mark plates are arranged can be downsized.
In addition, for example, with the scanning type exposure apparatus, in the case the first axis direction is the non-scanning direction of the substrate, by the first mark plate having approximately the size of the shot area on the substrate in this direction and a small size in the scanning direction, it becomes possible to form fiducial marks on the fiducial mark plate that can be measured at the same time with both eyes with a pair of mark detection system for masks that make up a twin lens which measures the mask alignment marks formed on both edges of the mask. Whereas, in the case the second axis direction is the scanning direction, by the second mask plate having approximately the size of the shot area in this direction and a small size in the non-scanning direction, it becomes possible to form fiducial marks on the fiducial mark plate that can be used for scaling adjustment of the interferometer which measures the position of the mask stage and the interferometer which measures the position of the substrate stage, which is performed using a single lens of the mark detection system for masks.
With the second exposure apparatus according to the present invention, at least three fiducial marks can be respectively formed on the substrate holding member.
According to the fourth aspect of the present invention, there is provided a third exposure apparatus which exposes a substrate with an energy beam and forms a predetermined pattern on the substrate, the exposure apparatus comprising: a substrate stage that moves two-dimensionally; a position measurement unit that measures a position of the substrate stage; a substrate holding member mounted on the substrate stage that holds the substrate; at least two fiducial marks including a first fiducial mark and a second fiducial mark which are arranged on a straight line passing through a center of the substrate holding member on opposite sides with respect to the center, and are arranged on the substrate stage with a positional relationship between each of the fiducial marks and the substrate holding member constant; a mark detection system which detects marks located on the substrate stage including the at least two fiducial marks; and a control unit that performs various types of measurement sequences respectively including a detection operation to detect either of one and a plurality of the at least two fiducial marks using the mark detection system and the position measurement unit.
With this exposure apparatus, since the first fiducial mark and the second fiducial mark are arranged on a straight line passing through the center of the substrate holding member on opposite sides with respect to the center, the interval between both fiducial marks can be about the diameter of the substrate holding member, therefore, limitations on the measurement span can be relaxed, allowing the measurement accuracy to be improved. In addition, the center of the substrate holding member lays on the straight line connecting both fiducial marks, therefore, in the case of obtaining the center of the substrate holding member based on the measurement results of the position of the fiducial marks, the central point corresponds, so to speak, to the interpolation point of the fiducial mark positions. Accordingly, the controller can, for example, detect the positional information on each fiducial mark arranged on the substrate stage by using the mark detection system and the position measurement, and by performing a predetermined calculation based on the positional information, the holding member coordinate system which origin is the center of the substrate holding member can be obtained with a sufficient level of reliability. Furthermore, the control unit obtains the positional information on the alignment marks that lie within the polygon on the substrate using the mark detection system and the position measurement unit based on an arbitrary coordinate system, such as the stage coordinate system, and converts the information to the positional information based on the holding member coordinate system. This allows the fiducial marks to be re-measured based on a new coordinate system, even in the case when the position of the substrate stage cannot be controlled temporarily, and based on the measurement results and the positional information based on the holding member coordinate system, the positional information on the alignment marks can be obtained with high reliability based on the new coordinate system. Accordingly, for similar reasons explained earlier, it becomes possible to control the position of the substrate with good accuracy at all times, without increasing the size of the substrate stage and the footprint of the apparatus. Also, in this case, since the two fiducial marks are symmetrical with respect to the center of the substrate holding member, it is possible, for example, to easily calculate the center coordinates and the rotational angle of the substrate holding member.
In this case, the exposure apparatus can further comprise: a plurality of fiducial mark plates arranged on a periphery of the substrate holding member on the substrate stage, on which one of the at least two fiducial marks is respectively formed.
In this case, at least two fiducial marks can be arranged on a plurality of fiducial mark plates, dispersed by each measurement sequence which uses any one of the fiducial marks.
In this case, a position of the substrate stage is controlled with the position measurement unit based on an orthogonal coordinate system, and the plurality of fiducial mark plates can include a first mark plate on which a plurality of fiducial marks including the first fiducial mark are arranged along a first axis direction of the orthogonal axis, the first mark plate narrowly extending in the first axis direction, and a second mark plate on which a plurality of fiducial marks including the second fiducial mark are arranged along a second axis direction orthogonal to the first axis, the second mark plate narrowly extending in the second axis direction.
With the third exposure apparatus according to the present invention, at least two fiducial marks can be respectively formed on the substrate holding member.
In addition, with the third exposure apparatus according to the present invention, a position of the substrate stage can be controlled with the position measurement unit based on an orthogonal coordinate system, and the straight line connecting the first fiducial mark and the second fiducial mark can be tilted at an angle of approximately 45xc2x0 with respect to both coordinate axes of the orthogonal coordinate system.
In such a case, since the straight line that connects the first fiducial mark and second fiducial mark has a tilt at an angle of approximately 45xc2x0 with respect to the coordinate axes of the orthogonal coordinate system, it becomes possible to measure the position of the mark with the accuracy of the same level in the direction of both axes in the orthogonal coordinate system.
In the detection operations of the fiducial marks with the exposure apparatus in the present invention, the positional information on the fiducial marks (for example, coordinate values on the orthogonal coordinate system which sets the movement of the substrate stage) does not necessarily have to be detected. For example, the fiducial marks may only be used for detection of the positional information (including the relative positional relationship with the fiducial marks) of marks formed on the mask or the mask stage or the like, or for detecting the optical properties (such as projection magnification) of the projection optical system. For example, the projection magnification of the projection optical system can be easily obtained by detecting the relative positional relationship between a plurality of marks formed on the mask or the mask stage and a plurality of fiducial marks corresponding to these marks formed on the substrate stage, or by detecting the positional relationship between a plurality of marks on the mask stage side, and the positional relationship between a plurality of fiducial marks on the substrate stage side. The correspondence of the mask coordinate system and the substrate coordinate system can also be obtained by detecting the relative positional relationship between a plurality of marks formed on the mask or the mask stage at a predetermined interval in a predetermined direction and a plurality of fiducial marks corresponding to these marks on the substrate stage.
Furthermore, fiducial marks on the substrate stage in the present invention refers not only to fiducial marks formed directly on the substrate stage and fiducial marks formed on mark plates fixed on the substrate stage, but also includes fiducial marks formed on the substrate holding member or on the mark plates fixed on the substrate holding member.